Four component optical objective



2,481,749- FOUR COMPONENT OITICAL OBJECTIVE Charles Gorrie Wynne. Bromley Hill, England, sie

signor to Wray (Optical Works) Limited, Bromley Hill. England. a Eritish company Application February 7. 1945, Serial No. 578,641- In Great Britain February 25. 1 944 sci-sims. (cl. sHnfjj photographic and like purposes having large relag ,im 707%/ I l This invention relates to optical lenses for tive apertures and corrected for spherical aberrations, coma, field curvature and astigmatism, distortion and chromatic aberrations. More particularly, it is concerned with the type of lens consisting of two meniscus components each having its concave surface of greater curvaturev than its convex surface and disposed adjacent to, one on each side .of. and concave to the aperture stop, and two convergent lenses, one on the side of each of the menisci remote from the stop, each of these convergent lenses being either a single lens or a cemented convergent member whose cemented surface, if dispersive, is not sulciently so to produce jointly with the immediately preceding surface an effectof relative overcorrection t of axialspherical aberration on a pencil of light incident on the front of the lens parallel to the axis.

Previous lenses of this type have had the meniscus components each consisting of two or more elements, either cemented together or with small air-spaces between them.

According to the present invention. a lens of the above type has one compound meniscus component and the other meniscus consisting of a single element which may be either the front or back meniscus in the sense that the front is that side of the lens facing the longer conjugate for which the lens is corrected. It is found that it is thus possible to make one cemented surface do the work of tw'o and to obtain equally good or even better correction with such a lens as with the previous lenses of this type already referred to.

A practical example of an objective in accordance with the invention is illustrated in the accompanying drawing.

In that drawing. the meniscus inthe f orm of a compound component a, b is the front meniscus v` l in the sense that the front is the side of the lens in the sense mentioned above. and the back meniscus is a. single element c placed on the opposite side of the aperture stop.. versent lens e and the back convergent lens l in this example are both single lenses.

Numerical data for this example are set out in Table A below in which n. rs r are the radii of curvature of the surfaces marked, a surface with convexity to the front being indicated as having a positive radius and a surface with concavity to the front as having a negative radius of curvature: di, da 3 da denote the axial thick- The front connumbernr- Tabled [aquivnmuniengzh-mo. mauvupmm rn.

' Thickness Refractive Abb? Element Radius or opann Index 'l 'Mm d om xoxo v.. l I

r. fasse l l '1 5:"

n +.ano d; .H62 Rs 1.610 1V. al

Q D n +.2059 de .027 ai 1.7m v d .2075 1| .m

. d. .m1 n. Lou V. sas

n -.soas 98m d10 n I da .0646 Il 1.613 Vl 51B The invention may be applied to lenses having separations between successive surfaces:

various additional features, apart from that of one of the convergent lenses e oral being a cemented member with a dispersive cemented surface of limited effect as already mentioned above. Thus. the single convergent lens e or l, either at the front or the back, may be replaced by two single lenses to enable the relative aperture to be increased. Again, cemented surfaces may be added either making the outside members cemented doublets or triplets.

In place of cemented surfaces, small air spaces bounded by surfaces of the same or slightly different radit of curvature may be provided.

Furthermore, the lens may be composed in part or entirely of the relatively recent high refractive index glasses or of the more normal glasses. One

or more of the lens elements may be formed o! I -1 transparent crystal; for example, .very good sec ondary spectrum correction may be obtained by using an alkali metal halide such as potassium bromide or iodide for the divergent element in the together with suitably cemented meniscus selected glasses for the other members.

Ie-...An

ns the mean refractive indices of the glasses used. and Vi. Va Vs their Abb V Finally, some of the surfaces maybe made tov depart slightly vfrom the spherical form.

I claim: f 'i l. An optical obiective comprising an aperture stop. a front meniscus component -of compound structure arranged on the front side of said aper. ture stop and having an outer concave surface l facing said stop with a radius oi' curvature of sul etantiai1y 0.2 times the equivalent focal lenth of the objective and an outer convex surface with a radius of curvature of substantially 0.3 times said focal length.' a single-element miniecus -f ass-1.749

component positioned at the back of said aperture stop in.axial alignment with said front meniscus component and having a concave Burface facing said stop with of substantially 0.26 times said focal length and an outer convex surface of a radius of substantially 0.3 times said focal length. a convergent.;v

a radius o! curvature' component arranged in front of said front meniscus, and a convergent component arranged in the rear of said back meniscus. 2. An optical objective according to claim 1 wherein said front mented doublet.

3. An optical objective according to claim 1 A wherein said front and rear convergent com-`- ponents are formed of singleq-element lenses and are substantially in contact with the convex sur-v meniscus is 'formed of a. ce-

faces of the front and back meniscus components.

4. A five-glass optical tive aperture not less than F/2.5 and consisting of an aperture stop, two meniscus components disposed adjacent to and concave to said aperture stop and one on each side of said aperture stop, one of said meniscus components being a ce mented doublet andthe other being a single glass element having a concave surface of a radius the radius of curvature of its convex surface which has a radius of curvature not less than 0.25 andnot more than 0.75 times the equivalent focal length of the objective. and two single objective having a relanot less than 0.52 and not more than 0.95 times' -l l glass convergent lenses, one on the side of each of said meniscus components remote from said aperture stop.

5. A fiveglass optical objective according to claim 4 wherein said cemented doublet has a con cave outer surface formed on a radius between 0.45 and 0.90 of the radius of curvature of its outer convex surface which has a radius of curvature between 0.20 and 0.60 of the equivalent focal length of the objective.

6. An optical objective comprising four axially aligned components including two meniscus components arranged on opposite sides of an aperture stop, each being concave to said stop and one being a cemented doublet. anda vpair of'com' the opposite-1:l said meniscus components from said.

versent components arranged on sides of aperture stop. said components having numerical wherein n. rs indicate the radii of the indi-iff',

vidual surfaces counting from the front. di. da. do. do. d. 'indicate the axial thicknesses of the` individual elements and da. axial air separations between the component;

' REFERENCES CITED" rile following refer file of this patent:

Great Britain Apr. 22, 1942 vi-sasl v di. d1 lndlcatetho CHARLES conm WYNNB.

ces are 'of record the- ..1 

